JSON format support

[guanucoluis]

I'm using pytelegraf library but I want to send JSON format to telegraf agent. Is possible to support it? I think the command could be this:

client.metric("IMU_Acel",{"x": imu.get_x, "y": imu.get_y(), "z": imu.get_z()},
tags={'server_name': 'my-server'},
"timestamp"= 1458229140))